The present invention relates generally to an apparatus for separating a one non-round sheet from a stack of identical sheets and particularly to an apparatus for separating film sheets used for photographic purposes.
More specifically, the invention relates to an apparatus which comprises a container with a recess for holding the stack, a base with a dispensing opening located beneath the container, a separating element with an aperture for receiving the bottom sheet that is to be separated from the stack, the separating element being located between the container and the base and being essentially a flat disc, the thickness of which is smaller than the thickness of a single sheet of the stack, and means for causing a relative rotation between the container and the separating element around an imaginary axis passing through the recess of the container. The dispensing opening of the base and the aperture of the separating element are capable of separating each bottom sheet from the stack and conveying the separated sheet into the dispensing opening of the base, and the recess of the container and the aperture of the separating element conform essentially in shape and size to one another and of the same shape and size of the sheets of the stack when viewed in the direction of the imaginary axis.
Apparatus of this general type are known, for example, from the German published patent application No. 24 45 338 and U.S. Pat. Nos. 4,013,193 and 2,503,239. These apparatus were previously used for removing a single object such as framed photographic slides from a stack of like objects. However, such objects are relatively thick in comparison to their size and are resistant to bending. Substantial difficulties arise if a device of the known type is used to separate a single sheet from a stack of relatively thin sheets that are only slightly resistant to bending, such as film sheets for photographic purposes, for example. The cited difficulties occur for the most part as a result of the gravitationally induced sagging of the middle or central portion of a thin sheet that is supported only by its corners. In such a situation, the corners of the sheet point diagonally upwards, which in general can severely hamper the separation and dispensing procedure produced by the relative rotation between the separating element and the container or even make the procedure quite impossible.
For the reasons described, apparatus of the type noted above have not been used previously for separating and dispensing relatively thin sheets that have little resistance to bending, such as photographic film sheets. Instead, apparatus have been used in which each sheet to be separated from the stack is moved parallel to an edge of the sheet by means of the separating element. As a consequence, the apparatus has a relatively long transport path for the sheet to be separated and a correspondingly large power requirement for the separation procedure. In addition, the long transport path necessitates corresponding large dimensions for the apparatus and the apparatus is therefore relatively bulky and heavy. To alleviate the above-noted disadvantages, apparatus have also been produced in which the sheet to be separated from the stack is folded during the separation procedure. This is disadvantageous in certain cases, however, because the separated sheet is no longer flat, which can lead to a dulled image if the sheet is a film sheet used for photographic purposes. In the better known apparatus for dispensing individual film sheets, there is, in addition, the danger that as a result of the relatively long transport path or the bending of the separated sheet, surface scratches and electric charges will occur. Such electric charges, as is well known, give rise to electrostatic forces, which in turn render handling of the separated sheet much more difficult and can attract dust particles which may lead to surface scratches on the separated sheet and to visible defects in the photographic image.